Altaya ALT95922 German Horch 108 Type 1A Command Car with 10.5cm le FE 18M Cannon - Artillerie Regiment 119, 11.Panzer Division, Kursk, Russia, 1943 (1:72 Scale)"The peril of the hour moved the British to tremendous exertions, just as always in a moment of extreme danger things can be done which had previously been thought impossible. Mortal danger is an effective antidote for fixed ideas."- Generalfeldmarschall Erwin Rommel

One of the problems presented by the original policy of purchasing commercially based vehicles for military usage was the vast diversity of makes taken on to the inventory, and the associated maintenance and spares supply problem. Different makes of engine, transmission, chassis, and so on meant that the stock of spares needed was immense. Thus, once the big armament program got under way, it was decided in 1934 to replace the range of commercially based chassis with a new range of standardised chassis types. It was intended that the three classes of field car, light, medium, and heavy, would have many parts in common, including suspension units, and that the light and heavy cars would have steerable wheels at the front and back, and would have four wheel drive. This proved to be too ambitious an ideal, even from the start, for the cost and time factor involved in developing such a sophisticated series of vehicles was immense. Only the early vehicles had rear wheel steering, and this requirement was dropped in 1940 to simplify production. Auto-Union/Horch were the main builders of both the medium and heavy passenger cars in the Einheits programme (einheitsfahrgestell: standard motor chassis).

The Auto Union/Horch Chassis I for heavy passenger cars (schwerer personenkraftwagen) was produced in 1935. As part of the overall plan it was intended to use this chassis with a rear mounted engine for armored cars and with a front mounted engine for passenger cars. The original chassis with steerable wheels front and back was designated I a, and the later production chassis (from 1939-40) was designated I b. The chassis featured four wheel drive. There was a torque converter with a limited differential action to prevent winding up in the transmission. The front axle was driven directly from the main gearbox, which included a third differential. There were five forward gear ratios, one reverse, and an auxiliary low gear for cross country work. There was a self locking differential on the rear axle with a normal differential at the front, this arrangement ensuring that all wheels received driving power no matter what the nature of the terrain. There was a fully independent suspension, each wheel having two radius arms sprung by two coil springs between the power radius arm and a bracket on the chassis frmae. Shock absorbers were incorporated into the suspension to prevent damage to the steering arms. The four wheel steering faciilty proved to be unsatisfactory in the long term. The rear wheel steering was optional, controlled by a dog clutch operated by a lever from the driving position. Using four wheel steering and driving fast, the vehicle was found to slew sideways; thus it was not popular and after some experience four wheel steering was forbidden altogether at speeds over 13 mph. This limitation made the whole facility of such slight value that it was dropped entirely from the 1940 onward production chassis.

Field car production with this chassis started late in 1938. Externally all Auto-Union/Horch heavy cars looked alike irrespective of actual chassis model, however. By 1940 the chassis had been simplified considerably, and the Berlin Ford factory was also by then engaged in production. Ford built vehicles had a Ford 3.6 litre V-8 78 hp engine in place of the Horch unit. The late 1940 models lacked recesses in the body and chassis mounted support arms for spare wheels. Production ceased in 1941 in favour of a new scheme under the Schell-Programm which sought to rationalise car production completely. In this scheme the heavy car shared the chassis of the 1.5 ton light truck. Auto-Union/Horch heavy cars remained in service throughout World War II, however, and were among the most common of German vehicles on every front. The Auto-Union/Horch on the heavy passenger car chassis was used in several roles, and though the layout of the open body followed the old Kubelsitzer idea, all but the very earliest had the added refinement of metal side doors rather than canvas side screens.